chore(envoy-gateway): Add version v1.6.0 (#585)

Author: nelsen129

libs/envoy-gateway/config.jsonnet

@@ -1,5 +1,10 @@
 local config = import 'jsonnet/config.jsonnet';
-local versions = ['v1.3.0', 'v1.4.0', 'v1.5.0'];
+local versions = [
+  'v1.3.0',
+  'v1.4.0',
+  'v1.5.0',
+  'v1.6.0',
+];
 
 config.new(
   name='envoy-gateway',